A customer recently asked this question. It may be of interest to others. “When mounting booklet panes, should you just mount the pane of stamps? Or do you need to include the booklet cover too?”
If you're keeping the entire booklet together, then traditional booklet collectors insist on having the cover too. Of course, that adds to the thickness and makes it a little more difficult to mount. A complete booklet (BK numbers in the Scott catalog) is all panes intact and the cover too.
If you're only interested in displaying a pane of stamps (and use up the other panes for postage, whatever), then displaying the pane without the cover is a better way to go. It will mount easier and it doesn't change the value.
One caution is that there are a couple of booklets where the entire booklet is more valuable.
For example, if there are 4 panes in a booklet and each pane has a catalog value of $2.50 but the entire booklet (BKxxx) has a catalog value of, say, $11 (approximately 4 times the individual panes), then you can be safe in removing one pane only and throwing away the cardboard cover. If there are 4 panes at $2.50 but the entire booklet is $50 in the catalog, it’s better to keep the entire booklet together. It’s more valuable as an entire booklet than it is as individual panes.